Changing Rarg[]minbucket can result in different variables being
chosen at different nodes. Compare the tree obtain with the command
above (with Rarg[]minbucket set to 100) to the result when
Rarg[]minbucket is set to 10. Note how node 7 was originally split
using Age but with the minimum bucket size set to 10 the
node is split on Deductions. We can see why -- the
resulting node 15 has only 30 entities:

Whilst the default is to set Rarg[]minbucket to be one third of
Rarg[]minsplit there is no requirement for Rarg[]minbucket to be
less than Rarg[]minsplit. A node will always have at least
Rarg[]minbucket entities, and it will be considered for splitting
if it has at least Rarg[]minsplit entities and on splitting, each
of its children have at least Rarg[]minbucket entities.